<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1 {
            width: 200px;
            height: 200px;
            border: 10px double red;
            /*设置边框, 值越大越圆,当超过宽高一半时为正圆*/
            /*border-radius: 200px;*/
        }

        #d2 {
            width: 100px;
            height: 100px;
            border: 1px solid red;
            /*给元素添加内边距 默认情况下会影响元素的显示范围*/
            padding-top: 50px;
            padding-left: 50px;
            /*添加完此样式后 外边距和边框不再影响宽高*/
            box-sizing: border-box;

        }

    </style>
</head>
<body>
<h1>这是h1</h1>
<p>这是段落标签</p>
<ul>
    <li>aaa</li>
    <li>bbb</li>
    <li>ccc</li>
</ul>
<input type="text">
<div id="d1">边框测试</div>
<div id="d2">内边距</div>
</body>
</html>